Systems and methods for purging an exhaust reductant delivery system

ABSTRACT

A hydraulic system comprises a fluid tank and a pump, including a pump reservoir, fluidly coupled to the tank via a supply line. A valve is in fluidic communication with the pump reservoir via a pressure line. A backflow line fluidly couples the pump reservoir to the fluid tank via a timer reservoir and an orifice included in the timer reservoir. The hydraulic system transitions between a normal state and a purge state. In the normal state in which the pump is on, a first portion of the fluid is communicated from the pump reservoir to the valve and a second portion of the fluid is communicated from the pump reservoir to the tank. In the purge state, the pressure line and valve are purged followed by the backflow line and the pump reservoir such that no fluid remains in the pump reservoir.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/555,052, filed Aug. 31, 2017, which is the U.S. National Stage of PCTApplication No. PCT/US2016/020678, filed Mar. 3, 2016, which claimspriority to and the benefit of U.S. Provisional Patent Application No.62/129,474, filed Mar. 6, 2015, the contents of which are incorporatedherein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates generally to hydraulic systems for usewith exhaust aftertreatment systems.

BACKGROUND

Exhaust aftertreatment systems are used to receive and treat exhaust gasgenerated by internal combustion (IC) engines. Conventional exhaust gasaftertreatment systems include any of several different components toreduce the levels of harmful exhaust emissions present in exhaust gas.For example, certain exhaust aftertreatment systems for diesel-poweredIC engines include a selective catalytic reduction (SCR) catalyst toconvert NOx (NO and NO₂ in some fraction) into harmless nitrogen gas(N₂) and water vapor (H₂O) in the presence of ammonia (NH₃).

Generally, an exhaust reductant (e.g., a diesel exhaust fluid such asurea) is injected into the aftertreatment system and mixed with theexhaust gas. The exhaust reductant can provide a source of ammonia tofacilitate at least partial reduction of the NOx gases included in theexhaust gas. The reduction byproducts of the exhaust gas are thenfluidly or fluidically communicated to the catalyst included in the SCRaftertreatment system. The catalyst decomposes substantially all of theNOx gases into relatively harmless byproducts, which are expelled out ofsuch conventional SCR aftertreatment systems.

Hydraulic systems are generally used to pump the liquid exhaustreductant into the SCR system. In conventional hydraulic systems, theexhaust reductant (e.g., a diesel exhaust fluid such as urea) cancrystallize at the tip of a doser or nozzle configured to communicatethe exhaust reductant into the SCR system. This restricts gas flow in apressure line coupled to the nozzle, which results in substantialnegative pressure and high vacuum. The high vacuum is equalized bypulling exhaust reductant from an exhaust reductant storage tankinstantaneously after completion of a purge of the system.

During purge, the system is filled with warm gas from the vehicle'sexhaust system. In cold weather conditions, after shutdown, the warmpurge gas cools downs, leading to volume shrinkage. This creates anegative pressure drawing exhaust reductant from the storage tank intothe pump after system shutdown. The exhaust reductant can freeze in thepump. The fluid's expansion when frozen can then lead to pumpmalfunctions and/or cracks.

SUMMARY

Embodiments described herein relate generally to hydraulic systems foruse with exhaust aftertreatment systems. In particular, variousembodiments relate to exhaust reductant delivery systems that include atimer reservoir and orifice configured to allow purging of a pressureline, backflow line and pump reservoir of the exhaust reductant deliverysystem on system shutdown. The purging is configured to ensure that noexhaust reductant remains in a pump reservoir after the system is shutdown. In particular embodiments, the orifice is configured to allowbi-directional flow of the exhaust reductant.

In a first set of embodiments, a hydraulic system comprises a fluid tankcontaining a fluid and a pump and a pump reservoir. A supply linefluidly couples the fluid tank to the pump. A valve is in fluidiccommunication with the pump reservoir. A pressure line fluidly couplesthe pump reservoir to the valve. The hydraulic system also includes atimer reservoir including an orifice, and a backflow line which fluidlycouples the pump reservoir to the fluid tank via the timer reservoir.

The hydraulic system is configured to transition between a normal stateand a purge state. In the normal state, the pump is on and a firstportion of the fluid is communicated from the pump reservoir to thevalve via the pressure line. A second portion of the fluid iscommunicated from the pump reservoir to the fluid tank through thebackflow line via the orifice and the timer reservoir. In the purgestate, a first negative pressure develops at an outlet of the pump. Thefirst negative pressure creates a second negative pressure in the pumpreservoir, the valve and the pressure line. The second negative pressurepurges the valve and the pressure line in a first time from pumpshutdown. Furthermore, a third negative pressure develops in thebackflow line. The third negative pressure draws the fluid from thebackflow line via the timer reservoir and the orifice into the pumpreservoir. The third negative pressure further draws air from the fluidtank into the pump reservoir such that the backflow line is purged in asecond time from pump shutdown, which is greater than the first time.The first negative pressure continues to draw the fluid from the pumpreservoir to the fluid tank and purges the pump reservoir with air for athird time after the backflow line is purged. The purging of the pumpreservoir vents the valve, the pressure line and the pump reservoir toatmospheric pressure such that no fluid remains in the pump reservoir.In particular embodiments, at least one of the timer reservoir, theorifice and the backflow line are structured such that the second timeis greater than the first time.

In a second set of embodiments, an apparatus for purging a hydraulicsystem comprises a fluid tank containing a fluid, a pump, a pumpreservoir, a supply line fluidly coupling the fluid tank to the pump, avalve in fluidic communication with the pump reservoir, and a pressureline fluidly coupling the pump reservoir to the valve, comprises a timerreservoir including an orifice. A backflow line fluidly couples the pumpreservoir to the fluid tank via the timer reservoir. The apparatus isconfigured to allow the hydraulic system to transition between a normalstate and a purge state. In the normal state, the pump is on and a firstportion of the fluid is communicated from the pump reservoir to thevalve via the pressure line. A second portion of the fluid iscommunicated from the pump reservoir to the tank through the backflowline via the orifice and the timer reservoir. In the purge state, afirst negative pressure develops at an outlet of the pump. The firstnegative pressure creates a second negative pressure in the pumpreservoir, the valve and the pressure line. The second negative pressurepurges the valve and the pressure line in a first time from pumpshutdown. A third negative pressure develops in the backflow line. Thethird negative pressure draws the fluid from the backflow line via thetimer reservoir and the orifice into the pump reservoir. The thirdnegative pressure further draws air from the fluid tank into the pumpreservoir such that the backflow line is purged in a second time frompump shutdown. The first negative pressure continues to draw the fluidto the fluid tank and purges the pump reservoir with air for a thirdtime after the backflow line is purged The purging of the pump reservoirvents the valve, the pressure line and the pump reservoir to atmosphericpressure such that no fluid remains in the pump reservoir. At least oneof the timer reservoir, the orifice and the backflow line are structuredsuch that the second time is greater than the first time.

In a third set of embodiments, a method of purging a hydraulic systemwhich comprises a fluid tank, a pump, a pump reservoir, a supply linefluidly coupling the fluid tank to the pump, a valve in fluidiccommunication with the pump reservoir, a pressure line fluidly couplingthe pump reservoir to the valve, a backflow line, a timer reservoir andan orifice comprises activating the pump so as to operate the hydraulicsystem in a normal state. The pump reservoir is fluidly coupled to thefluid tank through the timer reservoir and the orifice via the backflowline. A first portion of the fluid is communicated from the pumpreservoir to the valve via the pressure line. A second portion of thefluid is communicated from the pump reservoir to the tank through thebackflow line via the orifice and the timer reservoir. The pump isdeactivated so as to operate the hydraulic system in a purge state inwhich a first negative pressure develops at an outlet of the pump. Thefirst negative pressure creates a second negative pressure in the pumpreservoir, the valve and the pressure line. The second negative pressurepurges the valve and the pressure line in a first time from pumpshutdown. A third negative pressure develops in the backflow line. Thethird negative pressure draws the fluid from the backflow line via thetimer reservoir and the orifice into the pump reservoir. The thirdnegative pressure further draws air from the fluid tank into the pumpreservoir such that the backflow line is purged in a second time frompump shutdown, which is greater than the first time. The first negativepressure continues to draw the fluid to the fluid tank and purge thepump reservoir with air for a third time after the backflow line ispurged. The purging of the pump reservoir vents the valve, the pressureline and the pump reservoir to atmospheric pressure such that no fluidremains in the pump reservoir.

In a fourth set of embodiments, a control circuitry for controlling ahydraulic system so as to allow purging thereof, the hydraulic systemcomprising a fluid tank containing a fluid, a pump, a pump reservoir, asupply line fluidly coupling the fluid tank to the pump, a valve influidic communication with the pump reservoir, a pressure line fluidlycoupling the pump reservoir to the valve, a backflow line, a timerreservoir and an orifice, comprises a controller. The controller isconfigured to be operatively coupled to the hydraulic system and controlthe operation thereof so as allow the hydraulic system to transitionbetween a normal state and a purge state. In the normal state, thecontroller activates the pump such that a first portion of the fluid iscommunicated from the pump reservoir to the valve via the pressure line.A second portion of the fluid is communicated from the pump reservoir tothe tank through the backflow line via the orifice and the timerreservoir. In the purge state, the controller deactivates the pump suchthat a first negative pressure develops at an outlet of the pump. Thefirst negative pressure creates a second negative pressure in the pumpreservoir, the valve and the pressure line. The second negative pressurepurges the valve and the pressure line in a first time from pumpshutdown. Furthermore, a third negative pressure develops in thebackflow line. The third negative pressure drawing the fluid from thebackflow line via the timer reservoir and the orifice into the pumpreservoir. The third negative pressure further draws air from the fluidtank into the pump reservoir such that the backflow line is purged in asecond time from pump shutdown. The first negative pressure continues todraw the fluid to the fluid tank and purges the pump reservoir with theair for a third time after the backflow line is purged. The purging ofthe pump reservoir vents the valve, the pressure line and the pumpreservoir to atmospheric pressure such that no fluid remains in the pumpreservoir.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 is a schematic diagram of an embodiment of a hydraulic system ina normal state.

FIG. 2 is a schematic diagram of the hydraulic system of FIG. 1 in apurge state in which the pressure line is purging.

FIG. 3 is a schematic diagram of the hydraulic system of FIG. 1 in thepurge state in which the backflow line is purging.

FIG. 4 is a side cross-section image of one embodiment of a backflowconnector for use in the system of FIG. 1, wherein the backflowconnector includes a check valve which is removed before including thebackflow connector in the hydraulic system of FIG. 1.

FIG. 5 is an image of another embodiment of a backflow line for use inthe system of FIG. 1, wherein the backflow line is arranged in aracetrack configuration to allow a pressure line to be purged before thebackflow line is purged.

FIG. 6 is a plot of pressure curves after pump shutdown of a pressureline included in an exemplary hydraulic system substantially similar tothe hydraulic system of FIG. 1, which includes the backflow connector ofFIG. 4 with and without the check valve.

FIG. 7A is a plot of pressure profile after pump shutdown of a pressureline of a hydraulic system which includes a backflow connector having acheck valve and a plugged nozzle, and FIG. 7B is a plot of the pressureprofile on pump shutdown of the pressure line of the hydraulic system ofFIG. 7A but with the check valve removed from the backflow connector.

FIG. 8 is a schematic flow diagram of an example method of purging ahydraulic system.

Reference is made to the accompanying drawings throughout the followingdetailed description. In the drawings, similar symbols typicallyidentify similar components, unless context dictates otherwise. Theillustrative implementations described in the detailed description,drawings, and claims are not meant to be limiting. Other implementationsmay be utilized, and other changes may be made, without departing fromthe spirit or scope of the subject matter presented here. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, and designed in a wide variety ofdifferent configurations, all of which are explicitly contemplated andmade part of this disclosure.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Embodiments described herein relate generally to hydraulic systems andin particular, to exhaust reductant delivery systems that include atimer reservoir and orifice configured to allow purging of a pressureline, backflow line and pump reservoir of the exhaust reductant deliverysystem on system shutdown. The purging is configured to ensure that noexhaust reductant remains in a pump reservoir after the system is shutdown. In particular embodiments, the orifice is configured to allowbi-directional flow of the exhaust reductant.

Specific embodiments described herein provide a number of benefitsincluding, for example: (1) venting of a pressure line, a backflow lineand a pump reservoir of a hydraulic system to atmospheric pressure; (2)preventing any negative pressure from remaining in the pump reservoirafter the hydraulic system is shut down, thereby preventing any fluid(e.g., exhaust reductant) from being drawn into the pump reservoir aftershutdown to prevent fluid crystallization and pump malfunction; (3)providing desired purging characteristics by removing check valve from abackflow connector, providing a timing reservoir and/or adjusting lengthof the backflow line without using complex algorithms or electroniccontrols; and (4) allowing transformation of conventional hydraulicsystems to the hydraulic systems described herein with minimalmodifications.

FIGS. 1-3 are schematic block diagrams of a hydraulic system 100 forcommunicating measured amounts of a fluid in various operational states.In particular embodiments, the hydraulic system 100 can include anexhaust reductant delivery system configure to deliver metered amountsof the exhaust reductant to an aftertreatment system (not shown). Thehydraulic system 100 includes a fluid tank 102, a pump 104, a pumpreservoir 106, a valve 108, and a timer reservoir 110 including anorifice 112.

The fluid tank 102 is configured to store a volume of a fluid. Inparticular embodiments, the hydraulic system 100 can include an exhaustreductant delivery system. In such embodiments, the fluid tank 102stores a volume of an exhaust reductant formulated to facilitatereduction of an exhaust gas flowing through the aftertreatment system.For example, the exhaust gas can include a diesel exhaust gas and theexhaust reductant can include a diesel exhaust fluid. Such dieselexhaust fluids can include a source of ammonia, for example an aqueoussolution of urea (e.g., the diesel exhaust fluid available under thetrade name ADBLUE®).

The pump 104 is fluidly (also referred to as fluidically) coupled to thetank 102 via a supply line 101. The pump 104 is the prime moverconfigured to pump the fluid through a hydraulic circuit of thehydraulic system 100. The pump 104 includes a pump reservoir 106. Thepump reservoir 106 acts as a temporary store of the fluid and allowscontrolled metering of the fluid to the valve 108.

The valve 108 is in fluidic communication with the pump reservoir 106via a pressure line 103. The valve 108 includes a one way valve. Inparticular embodiments, the valve 108 can be included in an injector ordoser configured to communicate an exhaust reductant (e.g., urea) to anaftertreatment system. In such embodiments, the injector can alsoinclude a nozzle or doser tip (not shown) configured to communicate theexhaust reductant into the aftertreatment system.

The hydraulic system 100 also includes a timer reservoir 110 thatincludes an orifice 112. A backflow line 105 fluidly couples the pumpreservoir 106 to the fluid tank 102 via the time reservoir 110. In someembodiments, the backflow line 105 has a sufficient length (e.g., atleast 1.25 meters) such that backflow line 105 serves as the timerreservoir 110. In such embodiments, a backflow connector which includesthe orifice 112 can be included in the hydraulic system 100 for fluidlycoupling the backflow line 105 to the pump reservoir 106. In thismanner, the hydraulic system 100 forms a closed loop hydraulic circuit.Furthermore, end of the backflow line 105 coupled to the fluid tank 102is located within the fluid tank 102 so as to be positioned above asurface of the fluid contained within the fluid tank 102.

In particular embodiments, the orifice 112 does not include a checkvalve such that the orifice 112 allows bi-directional flow between thepump reservoir 106 and the fluid tank 102. For example, FIG. 4 is animage of a cross-section of a backflow connector 211 which can beincluded in the hydraulic system 100. The backflow connector 211includes an orifice 212 and a check valve assembly shown by the arrow Dwhich is removed from the backflow connector 211 before integrating thebackflow connector 211 into the hydraulic system 100. In this manner,the backflow connector 211, and thereby the orifice 212, can allowbi-directional flow between the pump reservoir 106 and the fluid tank102.

The hydraulic system 100 is configured to transition between a normalstate and a purge state. FIG. 1 shows the hydraulic system operating inthe normal state. In the normal state the pump 104 is on and the fluidis pumped from the fluid tank 102 by the pump 104 to the pump reservoir106. A first portion of the fluid is communicated from the pumpreservoir 106 to the valve 108 via the pressure line 103. For example,the first portion of the fluid can include a metered amount of exhaustreductant to be communicated to the aftertreatment system through thepressure line 103 and the valve 108.

A second portion of the fluid is communicated to the fluid tank 102through the backflow line 105 via the orifice 112 and the timerreservoir 110, as shown by the arrow A in FIG. 1. The second portion ofthe fluid is significantly smaller than the first portion of the fluid.For example, the second portion of the fluid can include excess amountof exhaust reductant remaining in the pump reservoir 106 after the firstportion of the exhaust reductant has been communicated through the valve108 to the aftertreatment system. The second portion of the fluid iscommunicated back to the fluid tank 102 through the backflow line 105 toprevent any excess exhaust reductant from remaining in the pumpreservoir 106.

When the hydraulic system 100 transitions into the purge state, a firstnegative pressure develops in the pump 104, and thereby an outletthereof. The first negative pressure creates a second negative pressurein the pump reservoir 106, the valve 108 and the pressure line 103. Thesecond negative pressure purges the valve 108 and the pressure line 103,in a first time period. Expanding further, when the first negativepressure develops, fluid is pulled towards the fluid tank 102 from thepump 104 via the supply line 101. The first negative pressure furtherleads to the second negative pressure in the pump reservoir 106, thepressure line 103 and the valve 108. The second negative pressure in thepressure line 103 serves to draw the fluid into the pump reservoir 106and purge the valve 108 and the pressure line 103, as shown by the arrowB in FIG. 2.

A third negative pressure develops in the backflow line, for examplebecause of the second negative pressure in the pump reservoir 106. Thethird negative pressure draws the exhaust reductant from the backflowline 105 via the timer reservoir 110 and the orifice 112 into the pumpreservoir 106. As the last of the fluid is pulled from the timerreservoir 110 and the orifice 112 into the pump reservoir 106, the thirdnegative pressure further draws air from the fluid tank 102 into thepump reservoir 106. This purges the backflow line 105 in a second timeperiod. The timer reservoir 110, the orifice 112 and/or the backflowline 105 are configured such that the second time period is greater thanthe first time period, as described herein. In other words, the pressureline 103 and the backpressure line 105 start purging at the same time,but the pressure line 103 is purged first within the first time period,while the backflow line 105 continues to be purged after the pressureline 103 is purged until the end of the second time period.

In some embodiments, the timer reservoir 110 is configured to contain avolume of the fluid to allow the backflow line 105 to be purged afterthe pressure line 103 is purged. In such embodiments, the timerreservoir 110 serves as a hydraulic timer to provide a delay in thepurging of the backflow line 105 relative to the pressure line 103. Inother embodiments, the orifice 112 can have a diameter configured toallow the backflow line 105 to be purged after the pressure line 103 ispurged. The diameter of the orifice, the volume of the timer reservoir110, and the viscosity of the fluid can allow timing the purging of thebackflow line 105 such that the backflow line 105 purges after thepressure line 103 is purged. For example, the second negative pressurein the pressure line 103 and the valve 108 can change from a relativelylow value to a relatively high value as the last of the fluid is pulledinto the pump reservoir 106 through the orifice 112 and the less viscousair passes through the orifice 112 (as described herein in furtherdetail with reference to FIG. 6).

In still other embodiments, the backflow line 105 can be configured tohave a length to allow a sufficient volume of the fluid to be containedin the backflow line 105 such that the pressure line 103 purges beforethe backflow line 105. For example, the length can be such that thebackflow line 105 purges after the pressure line 103 regardless ofwhether a nozzle or doser tip for delivering the exhaust reductantsystem to the aftertreatment system is clear, or blocked with exhaustreductant deposits. FIG. 5 shows an exemplary backflow line 205 whichcan be used in the hydraulic system 100. The backflow line 205 isarranged in a racetrack configuration such that the backflow line 205can be compactly positioned within a hydraulic system (e.g., thehydraulic system 100). In order to ensure that the order of emptying ismaintained, the volume of the timer reservoir 110 is designed toencompass pressure line emptying under restricted gas entry from thedoser/nozzle. The ratio between the volume of the backflow line 105 andthe pressure line 103 is inversely proportional to the diameter of theorifice 112. In a particular embodiment, this ratio is in the range of30-35% inclusive (e.g., 33%). The volume of the backflow line 105 may becontrolled by changing the line's length or diameter.

After the backflow line 105 is purged, the first pressure continues todraw the fluid from the pump reservoir 106 to the fluid tank 102 topurge the pump reservoir with the air for a third time period after thebackflow line 105 is purged. The purging of the pump reservoir 106 withair from the fluid tank 102 vents the valve 108, the pressure line 103and the pump reservoir 106 to atmospheric pressure such that the nofluid remains in the pump reservoir 106. In other words, the hydraulicsystem 100 is calibrated such that the pressure line 103 is purgedbefore the backflow line 105, and after the backflow line 105 is purgedthere is sufficient negative pressure (e.g., the first negativepressure) in the hydraulic system 100 to continue purging the pumpreservoir 106 until no fluid remains in the pump reservoir 106. Thepurging of the pump reservoir 106 with the air from the fluid tank 102equalizes the pressure in the system to near ambient pressure such thatno negative pressure remains in the system for drawing any fluid fromthe fluid tank 102 into the pump reservoir 106 after the pump 104 isshut down.

In this manner, no fluid remains in the pump reservoir 108 after thepump is shut down. Thus, there is no opportunity for the fluid to freezein the pump reservoir 106 under cold conditions, thereby eliminatingpump malfunction and failure. In certain embodiments, the pumpingduration is adjusted to account for purging of the backflow line 105before the pressure line 103.

FIG. 6 includes plots of pressure profiles in the pressure line includedin a hydraulic system on shutting down of pump included in the hydraulicsystem. The hydraulic system can be substantially similar to thehydraulic system of FIG. 1-3. The hydraulic system was used to pumpdiesel exhaust fluid. The hydraulic system includes the backflowconnector of FIG. 4 having an orifice with and without a check valve.The pressure profiles of the pressure line for the hydraulic systemincluding the backflow connector with check valve and a doser (i.e.,nozzle of an injector) open, and including backflow connector withoutcheck valve and having the doser open (i.e., not plugged with dieselexhaust fluid deposits) are similar. However, the pressure in thepressure line included the hydraulic system that includes the backflowconnector without the check valve equilibrates to near atmosphericpressure after an initial negative pressure much earlier than the systemwith the backflow connector that includes the check valve.

As seen in FIG. 6, when the check valve is present and the doser isplugged, the pressure in the pressure line falls to a substantialnegative pressure of −50 kPa and remains at this pressure for aprolonged period of time even after the pump is shut down. Thisprolonged negative pressure leads to drawing of the exhaust reductantinto the pump reservoir after the pump is shut down which isdetrimental, as described herein.

In contrast, when the check valve is absent and the doser is plugged,the negative pressure is generated in the pressure line until time T1.This time is controlled by the pressure difference across the orifice,the size (e.g., diameter) of the orifice and/or the viscosity of thefluid flowing through the orifice. In this manner, the timer reservoirand the orifice can be used as a timer to allow the pressure line to bepurged before the backflow line. Time T1 is sufficient to allow thepressure line to be purged and corresponds to the time at which the lastof the diesel exhaust fluid is drawn into pump reservoir. At this time,the less viscous air drawn from the tank passes through the orificewhich allows the negative pressure in the pressure line to rise to nearambient (from −50 kPa to −10 kPa). In other words, the time point T1represents a change in an operating state of the hydraulic system whereprior to T1, the hydraulic circuit of the system is primarily purgingthe pressure line, and after T1 the hydraulic circuit is primarilypurging the pump assembly. After the pump shutdown, the open orificecontinues to draw air and effectively vents the pump reservoir andpressure line to ambient thereby preventing any negative pressure inthese components that might otherwise pull the exhaust reductant backinto the pump reservoir.

FIGS. 7A and 7B show various pressure profiles of a pressure line atvarious operational state of a hydraulic system that includes the timerreservoir and the orifice with and without the check valve in moredetail. FIG. 7A shows the pressure profiles at various operational stateof the hydraulic system that includes the orifice with the check valveand the doser plugged. Once the pump is shut down, significant negativepressure develops in the pressure line. The negative pressure (about −50kPa) is maintained for a prolonged time which urges a backflow of theexhaust reductant from the tank to the pump reservoir after pumpshutdown.

In contrast, when the check valve is removed from the orifice and thedoser is plugged, negative pressure (about −50 kPa) develops in thepressure line until the pressure line is purged when the pump is shutdown. The pressure line is completely purged by time T1. The backflowline continues to be purged until time T2 beyond the purging of thepressure line. The pressure drops to about (−10 kPa) by time T3 whilethe pump reservoir continues to be purged. By time T4, the system iscompletely purged and the pressure in the system rises to nearatmospheric pressure.

FIG. 8 is a schematic flow diagram of an example method 300 of purging ahydraulic system (e.g., the hydraulic system 100). The hydraulic systemcomprises a fluid tank (e.g., the fluid tank 102), a pump (e.g., thepump 104), a pump reservoir (e.g., the pump reservoir 106), a supplyline (e.g., the supply line 101) fluidly coupling the fluid tank to thepump, a valve (e.g., the valve 108) in fluidic communication with thepump reservoir, and a pressure line (e.g., the pressure line 103)fluidly coupling the pump reservoir to the valve.

The method 300 comprises providing a timer reservoir including anorifice at 302. The pump reservoir is fluidly coupled to the fluid tankthrough the time reservoir via a backflow line at 304. For example, thetimer reservoir 110 including the orifice 112/212 is provided. The pumpreservoir 106 is fluidly coupled to the fluid tank 102 through the timerreservoir 110 via the backflow line 105/205.

The pump is activated so as to operate the hydraulic system in a normalstate at 306. In the normal state, a first portion of the fluid iscommunicated from the pump reservoir to the valve via the pressure line.Furthermore, a second portion of the fluid is communicated from the pumpreservoir to the tank through the backflow line via the orifice and thetimer reservoir.

The pump is deactivated so as to operate the hydraulic system in a purgestate at 308. In the purge state, a first negative pressure develops inthe pump and a line connecting the pump to the pump reservoir. In someembodiments, a direction of rotation of the pump may be reversed so asto create the first negative pressure or otherwise increase a magnitudeof the first negative pressure. The first negative pressure creates asecond negative pressure in the pump reservoir, the valve and thepressure line. The second negative pressure purges the valve and purgesthe pressure line in a first time from pump shutdown, as describedbefore

A third negative pressure develops in the backflow line. The thirdnegative pressure draws the exhaust reductant from the backflow line viathe timer reservoir and the orifice into the pump reservoir. The thirdnegative pressure further draws air from the fluid tank into the pumpreservoir such that backflow line is purged in a second time from pumpshutdown. The first negative pressure continues to draw the fluid to thefluid tank so as to purge the pump reservoir with the air for a thirdtime after the backflow line is purged. The purging of the pumpreservoir vents the valve, the pressure line and the pump reservoir toatmospheric pressure such that no fluid remains in the pump reservoir.

The timer reservoir (e.g., the timer reservoir 110), the orifice (e.g.,the orifice 112/212) and/or the backflow line (e.g., the backflow line105/205) are structured such that the second time is greater than thefirst time. For example, the timer reservoir may be configured tocontain a volume of the fluid to allow the backflow line to be purged inthe second time.

In some embodiments, the orifice has a diameter configured to allow thebackflow line to be purged in the second time. The orifice may allowbi-directional flow of the fluid. For example, the orifice may notinclude a check valve so that the fluid can flow back and forth betweenthe fluid tank and the pump reservoir.

In some embodiments, the pressure line has a first length and thebackflow line has a second length longer than the first length. Thesecond length may be configured to allow the backflow line to be purgedin the second time. For example, a ratio between a backflow line volumeof the backflow line and a pressure line volume of the pressure line isin the range of 30% to 35% inclusive of all ranges and valuestherebetween. Furthermore, an end of the backflow line coupled to thefluid tank may be located within the fluid tank so as to be positionedabove a surface of the fluid contained within the fluid tank.

Any of the operations included in the method 300 or any other methoddescribed herein may be performed by a control circuitry which maycomprise, for example a controller. The control circuitry may beoperatively coupled to the hydraulic system 100 or any other hydraulicsystem described herein so as to control the operation thereof, forexample allow a purging thereof, as described herein. The controller maycomprise a memory such as a non-transitory computer readable medium,storing instructions or algorithms corresponding to the operations ofthe method 300. The controller may also include a processor forinterpreting and executing the instructions or algorithms stored in thememory. The controller may also include a sensor (e.g., for sensingvarious parameters of the hydraulic system) and/or transceiver (e.g.,for communicating signals to the hydraulic system (e.g., the pump 104 ofthe hydraulic system 100). In various embodiments, the controller mayalso include one or more circuitries to control the operation of thepump or other components included in the hydraulic system.

As used herein, the singular forms “a”, “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, the term “a member” is intended to mean a single member or acombination of members, “a material” is intended to mean one or morematerials, or a combination thereof.

As used herein, the terms “about” and “approximately” generally meanplus or minus 10% of the stated value. For example, about 0.5 wouldinclude 0.45 and 0.55, about 10 would include 9 to 11, about 1000 wouldinclude 900 to 1100.

The terms “coupled,” “connected,” and the like as used herein mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent) or moveable (e.g., removableor releasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

It is important to note that the construction and arrangement of thevarious exemplary embodiments are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein. Othersubstitutions, modifications, changes and omissions may also be made inthe design, operating conditions and arrangement of the variousexemplary embodiments without departing from the scope of the presentinvention.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment. Similarly, the use of theterm “implementation” means an implementation having a particularfeature, structure, or characteristic described in connection with oneor more embodiments of the present disclosure, however, absent anexpress correlation to indicate otherwise, an implementation may beassociated with one or more embodiments.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

1. (canceled)
 2. A system comprising: a pump fluidly coupled to a tankand configured to receive reductant from the tank, the pump operablebetween a normal state and a purge state; a pump reservoir fluidlycoupled to the pump and configured to receive the reductant from thepump and to provide the reductant to the pump; and a valve of aninjector or a doser, the valve fluidly coupled to the pump reservoirsuch that the valve is separated from the pump by the pump reservoir andconfigured to receive the reductant from the pump reservoir and toprovide the reductant to the pump reservoir; wherein the pump isconfigured to provide the reductant received from the tank to the pumpreservoir when the pump is in the normal state; and wherein the pump isconfigured to create a first negative pressure in the pump reservoirwhen the pump is in the purge state.
 3. The system of claim 2, whereinthe pump is configured to create a second negative pressure in the valvewhen the pump is in the purge state.
 4. The system of claim 2, whereinthe pump reservoir is configured to provide the reductant received fromthe pump to the pump when the pump is in the purge state.
 5. The systemof claim 2, wherein the valve is configured to receive the reductantfrom the pump reservoir when the pump is in the normal state.
 6. Thesystem of claim 5, wherein the valve is configured to provide thereductant from the pump reservoir to the pump reservoir when the pump isin the purge state.
 7. The system of claim 2, further comprising a timerreservoir fluidly coupled to the pump reservoir such that the timerreservoir is separated from the pump by the pump reservoir andconfigured to receive the reductant from the pump reservoir and toprovide the reductant to the pump reservoir.
 8. The system of claim 7,wherein: the timer reservoir is fluidly coupled to the tank; the timerreservoir is configured to provide the reductant received from the pumpreservoir to the tank when the pump is in the normal state; and thetimer reservoir is configured to provide the reductant received from thepump reservoir to the pump reservoir when the pump is in the purgestate.
 9. A method of operating a system including a tank, a pumpfluidly coupled to the tank and operable between a normal state and apurge state, a pump reservoir fluidly coupled to the pump, a valve of aninjector or a doser, the valve fluidly coupled to the pump reservoir,and a timer reservoir fluidly coupled to the pump reservoir, the methodcomprising: receiving, by the pump, reductant from the tank when thepump is in the normal state; receiving, by the pump reservoir, thereductant from the pump when the pump is in the normal state; providing,by the pump reservoir, the reductant to the pump when the pump is in thepurge state; receiving, by the valve, the reductant from the pumpreservoir when the pump is in the normal state; providing, by the valve,the reductant to the pump reservoir when the pump is in the purge state;and creating, by the pump, a first negative pressure in the pumpreservoir when the pump is in the purge state.
 10. The method of claim9, further comprising creating, by the pump, a second negative pressurein the valve when the pump is in the purge state.
 11. The method ofclaim 9, further comprising: receiving, by the timer reservoir, thereductant from the pump reservoir when the pump is in the normal state;and providing, by the timer reservoir, the reductant to the tank whenthe pump is in the normal state.
 12. The method of claim 11, furthercomprising: receiving, by the timer reservoir, the reductant from thetank when the pump is in the purge state; and providing, by the timerreservoir, the reductant to the pump reservoir when the pump is in thepurge state.
 13. The method of claim 12, further comprising: creating,by the pump, a second negative pressure in the valve when the pump is inthe purge state; and creating, by the pump, a third negative pressure inthe timer reservoir when the pump is in the purge state.
 14. The methodof claim 9, wherein the valve and the timer reservoir receive thereductant from the pump reservoir simultaneously.
 15. The method ofclaim 9, wherein the valve and the timer reservoir provide the reductantto the pump reservoir simultaneously.
 16. The method of claim 9, furthercomprising: emptying the valve of the reductant when the pump is in thepurge state; and emptying the timer reservoir of the reductant when thepump is in the purge state.
 17. The method of claim 16, furthercomprising emptying the pump reservoir of the reductant when the pump isin the purge state and after the valve has been emptied of the reductantand the timer reservoir has been emptied of the reductant.
 18. Themethod of claim 16, wherein: the valve is emptied over a first period oftime; the timer reservoir is emptied over a second period of time; andthe second period of time is greater than the first period of time.